1. Field of the Invention
The present invention relates generally to communication internetworking, and more specifically, to forwarding signals within a communications network.
2. Related Art
With the advent of the World Wide Web (WWW), global computer networks have quickly become cost-effective and reliable mediums for the exchange and management of information within an extensive array of computers and smaller computer networks. The computer networks vary in size and type such as, local internets, corporate intranets, local area networks (LAN), wide area networks (WAN), private enterprise networks, and the like. The global Internet is the most commonly known global computer network.
The evolution of global computer networks and supporting technologies has made it possible for government officials, educational institutions, businesses, nonprofit organizations, and individuals to communicate with the local networks or personal computers of other persons or organizations. The recreational and entertainment industries are also using global computer networks to expand their potential customer bases. As a result, more individuals and companies are using the Internet, for example, to transmit and/or multicast content for a variety of personal and business reasons. For example, a recording company may broadcast a live concert over the Internet to subscribers. As another example, a television production company may multicast a televised show over the Internet to a group of subscribers.
As more individuals and/or organizations take advantage of global networks to multicast content to a group of subscribers, greater emphasis must be placed on designing a distribution network capable of handling periods of heavy traffic. In a conventional multicast Internet exchange, a network of routers is provided to transport the multicast content from a host-server to the client members of a group. Typically, the multicast packets are transmitted to every available router within a virtual local area network (VLAN). Upon receipt of the multicast packets, the routers must determine the destination and forward the packets downstream to the next router or client end station.
Flooding multicast traffic to every port within a VLAN is not the most efficient or cost-effective way to forward multicasts. As such, some multicast protocols have been developed to limit the multicast traffic to a few select ports within a VLAN. The ports are selected by determining whether the port communicates directly or indirectly with a client group member. An example of such a limited multicast protocol is described in Experimental Internet Protocol Standard, Request for Comments (RFC) 2362 (Internet Architecture Board) as Protocol Independent Multicast (PIM) Sparse Mode (SM).
However, even with a limited multicast protocol, there exists no conventional method for quickly, efficiently, and inexpensively forwarding a multicast packet by a layer 2 switch. The term “layer” is used herein to refer to, for example, a layer of the Open Systems Interconnection (OSI) seven-layer Reference Model. As apparent to one skilled in the relevant art(s), a layer 2 switch operates at the data link layer or layer 2 as defined by the OSI Reference Model. At layer 3 or network layer, as defined by the OSI Reference Model, forwarding activity is performed by a router.
Commercially available switches, such as those available from Cisco Systems, Inc., create a special label or tag for multicast packets. Although tag switching enables a router to read the tag and forward the packet, the router must be specially configured to be able to interpret the tag. A hub, a commonly used layer 2 device, broadcasts traffic to all interfaces. This is expensive in terms of bandwidth usage, and inefficient as traffic is sent unnecessarily to interfaces or networks that may not require the traffic, thereby wasting network and CPU resources.
Other conventional network devices, such as routers, use the network layer to route and forward multicasts. Layer 3 processing requires additional processing time and memory. As such, like tag switching, the routing device must be specially configured to implement these processing requirements.
Therefore, a method and system are needed to address the above problems, and provide layer 2 processing to forward multicast packets efficiently and quickly.